1. Field of the Invention
The present invention relates to an information processor and method therefor. More particularly, the invention relates to an information processor which uses a narrower transmission band while controlling image quality deterioration in image data transmission and a method therefor.
2. Description of the Related Art
In digital video communication, images are usually transmitted in a compressed state because of limited bandwidth. Two different methods may be employed to compress images: intra-frame compression using relevance between images; and inter-frame compression using no relevance between images.
An Example of intra-frame compression is the moving picture experts group (MPEG) system. In the intra-frame compression system, a high compression ratio can be achieved by assigning data only to portions with changes among images. If, however, there is an error in the data, influence thereof may continue for a while.
An Example of inter-frame compression is the joint photographic experts group (JPEG) 2000 system. The inter-frame compression system does not utilize correlation and therefore is inferior to the intra-frame compression system in terms of compression ratio. However, if there is an error in the data, the error in the data has not effect outside of the image of interest.
Recently, there has been an increasing demand for transmitting multimedia data with a short delay time via the Internet or other transmission lines. An Exemplary application thereof is a remote operation system in which two remote medical facilities are connected by, for example, the Internet. Operation scenery in an operating room in one of the facilities is transmitted as moving images to a remote operating room in the other of the facilities, where an operator manipulates surgical instruments looking at incoming moving images. In such an application, it is necessary to transmit the moving images with a delay time not longer than several frame intervals.
In order to meet such a demand, Japanese Unexamined Patent Application Publication No. 2007-311924 discloses a system of compression encoding through wavelet transformation in which several lines in each picture of the moving image are considered as a compression encoding block. In the disclosed system, the encoding device can start compression encoding before all the data in the picture is input. If the compressed data is transmitted via a network and is decoded by a receiver side, the decoding device can start decoding before all the data in the picture is received. Accordingly, if the network propagation delay time is sufficiently short, real-time moving image transmission with a delay time shorter than a frame interval can be provided.